U.S. patent application number 14/486004 was filed with the patent office on 2015-03-19 for electrophoretic display apparatus and electronic apparatus.
The applicant listed for this patent is Seiko Epson Corporation. Invention is credited to Katsunori Yamazaki.
Application Number | 20150077836 14/486004 |
Document ID | / |
Family ID | 52667753 |
Filed Date | 2015-03-19 |
United States Patent
Application |
20150077836 |
Kind Code |
A1 |
Yamazaki; Katsunori |
March 19, 2015 |
ELECTROPHORETIC DISPLAY APPARATUS AND ELECTRONIC APPARATUS
Abstract
In at least one embodiment of the disclosure, an electrophoretic
display apparatus includes a first substrate. A refractive index
variation layer is arranged so as to oppose the first substrate. An
electrophoretic layer is arranged between the first substrate and
the refractive index variation layer. A refractive index of the
refractive index variation layer increases as it recedes away from
the electrophoretic layer in a thickness direction of the
electrophoretic layer.
Inventors: |
Yamazaki; Katsunori;
(Matsumoto-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Seiko Epson Corporation |
Tokyo |
|
JP |
|
|
Family ID: |
52667753 |
Appl. No.: |
14/486004 |
Filed: |
September 15, 2014 |
Current U.S.
Class: |
359/296 |
Current CPC
Class: |
G02F 1/1677 20190101;
G02F 2001/133565 20130101; G02B 26/026 20130101; G02F 1/167
20130101; G09G 3/34 20130101; G02F 1/133524 20130101; G02B 26/02
20130101; G09G 3/344 20130101; G02F 1/133502 20130101; G02F
2001/133562 20130101; G09G 3/36 20130101; G02F 1/1326 20130101;
G02F 1/1681 20190101 |
Class at
Publication: |
359/296 |
International
Class: |
G02F 1/167 20060101
G02F001/167; G02F 1/1335 20060101 G02F001/1335 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 18, 2013 |
JP |
2013-192665 |
Claims
1. An electrophoretic display apparatus comprising: a first
substrate; a refractive index variation layer having a refractive
index, the refractive index variation layer arranged so as to
oppose the first substrate; and an electrophoretic layer arranged
between the first substrate and the refractive index variation
layer, wherein the refractive index of the refractive index
variation layer increases as it recedes away from the
electrophoretic layer in a thickness direction of the
electrophoretic layer.
2. The electrophoretic display apparatus according to claim 1,
wherein the refractive index in the refractive index variation
layer continuously changes along the thickness direction.
3. The electrophoretic display apparatus according to claim 1,
wherein the refractive index gradually increases as it recedes away
from the electrophoretic layer.
4. The electrophoretic display apparatus according to claim 1,
further comprising: a second substrate and wherein the refractive
index variation layer is disposed between the electrophoretic layer
and the second substrate.
5. The electrophoretic display apparatus according to claim 1,
further comprising: a second substrate that is disposed between the
electrophoretic layer and the refractive index variation layer.
6. The electrophoretic display apparatus according to claim 5,
wherein the refractive index variation layer comprises a substrate
material and a plurality of discotic liquid crystal molecules
arranged in a predetermined oriented state in the substrate
material, and the refractive index of the refractive index
variation layer is substantially the same as a refractive index of
the second substrate.
7. The electrophoretic display apparatus according to claim 1,
wherein the refractive index variation layer includes a refractive
index anisotropic material which has a refractive index
anisotropy.
8. The electrophoretic display apparatus according to claim 7,
wherein the refractive index anisotropic material is a discotic
liquid crystal.
9. The electrophoretic display apparatus according to claim 8,
wherein the discotic liquid crystal includes molecules and the
molecules are vertically oriented near the electrophoretic layer
and are horizontally oriented in the thickness direction away from
the electrophoretic layer.
10. An electrophoretic display apparatus according to claim 1,
further comprising: a common electrode arranged between the
refractive index variation layer and the electrophoretic layer, and
wherein the first substrate is arranged opposite to an image
display surface and includes pixel electrodes facing the common
electrode.
11. An electronic apparatus comprising the electrophoretic display
apparatus according to claim 1.
12. An electrophoretic display apparatus comprising: a first
substrate; a light guide member arranged so as to oppose the first
substrate; and an electrophoretic layer arranged between the first
substrate and the light guide member, wherein the light guide
member is configured to pass a light reflected in the
electrophoretic layer in a thickness direction of the
electrophoretic layer.
13. The electrophoretic display apparatus according to claim 12,
wherein the light guide member comprises a plurality of bundled
optical fibers.
14. The electrophoretic display apparatus according to claim 13,
wherein a refractive index at a central part of each of the
plurality of bundled optical fibers is greater than a refractive
index at a peripheral part of each of the plurality of bundled
optical fibers.
15. The electrophoretic display apparatus according to claim 12,
further comprising: a second substrate and wherein the light guide
member is disposed between the electrophoretic layer and the second
substrate.
16. The electrophoretic display apparatus according to claim 12,
further comprising: a second substrate that is disposed between the
electrophoretic layer and the light guide member.
17. An electronic apparatus comprising the electrophoretic display
apparatus according to claim 12.
Description
CROSS-REFERENCE
[0001] The present application claims priority from Japanese Patent
Application No. 2013-192665 filed on Sep. 18, 2013, which is hereby
incorporated by reference in its entirety.
BACKGROUND
[0002] An electrophoretic display apparatus acquired by pouring
dispersion liquid in which electrophoretic particles are dispersed
into areas divided by walls which are formed between a pair of
substrates are known (for example, refer to JP-A-2013-7985).
[0003] However, when a certain pixel is focused as a target pixel,
the brightness of the target pixel changes due to the colors
(reflectance) of peripheral pixels, and thus there is a problem in
that display irregularity occurs.
SUMMARY
[0004] In at least one embodiment, an electrophoretic display
apparatus and an electronic apparatus capable of acquiring
excellent display quality by suppressing display irregularity may
be obtained.
[0005] The inventors, as a result of earnest research, have found
that a reason for change in the brightness of a target pixel due to
the colors (reflectance) of peripheral pixels is that approximately
60% of reflection light in the peripheral pixels is reflected in a
substrate surface and then radiated to the target pixel, and thus
the target pixel reflects the light. That is, if the peripheral
pixels are black, the amount of light which is radiated to the
target pixel decreases, and thus the target pixel becomes dark,
and, if the peripheral pixels are white, the amount of light which
is radiated to the target pixel increases, and thus the target
pixel becomes bright. That is, knowledge in that optical crosstalk
causes the display irregularity to occur has been acquired.
Embodiments are based on this research.
[0006] According to at least one embodiment, an electrophoretic
display apparatus includes a first substrate, an electrophoretic
layer that is arranged on one surface side of the first substrate,
a refractive index variation layer that is arranged on the
electrophoretic layer. The refractive index variation layer is
configured to change such that a refractive index gradually
increases while receding from the electrophoretic layer in a
thickness direction of the electrophoretic layer.
[0007] In the electrophoretic display apparatus according to this
embodiment, when light at a greater than a critical angle in light
scattered in the electrophoretic layer passes through the
refractive index variation layer, light can be bent in a normal
line direction (thickness direction of the electrophoretic layer).
Therefore, it is possible to reduce light which is totally
reflected and radiates adjacent pixels when light does not pass
through the refractive index variation layer. Therefore, display
irregularity due to optical crosstalk may be prevented from
occurring, and thus it is possible to perform display with a higher
quality.
[0008] According to this embodiment, in the refractive index
variation layer, the refractive index may continuously change.
[0009] In the electrophoretic display apparatus, since the
refractive index of the refractive index variation layer
continuously changes, a boundary surface is not generated in the
refractive index variation layer. Therefore, light is not reflected
in the boundary surface in the refractive index variation layer.
Therefore, light passes through the refractive index variation
layer, and is effectively taken to the outside.
[0010] According to the aspect, the electrophoretic display
apparatus may further include a second substrate that interpose the
electrophoretic layer between the first substrate and the second
substrate, and the refractive index variation layer may be arranged
between the electrophoretic layer and the second substrate.
[0011] In the electrophoretic display apparatus, it is possible to
cause light from the electrophoretic layer to be efficiently
incident into the refractive index variation layer.
[0012] According to this embodiment, the electrophoretic display
apparatus includes a second substrate that interposes the
electrophoretic layer between the first substrate and the second
substrate. The refractive index variation layer may be provided on
the second substrate on a side opposite to the electrophoretic
layer.
[0013] In the electrophoretic display apparatus, since the
refractive index variation layer is arranged on the second
substrate, it is possible to prevent the second substrate from
being damaged or the like.
[0014] According to this embodiment, the refractive index variation
layer may include a refractive index anisotropic material which has
a refractive index anisotropy.
[0015] In the electrophoretic display apparatus, light from the
electrophoretic layer may be securely bent, and thus it is possible
to efficiently take light to the outside.
[0016] According to this embodiment, the refractive index
anisotropic material may be a discotic liquid crystal.
[0017] In the electrophoretic display apparatus, it is possible to
cause light from the electrophoretic layer to be effectively
refracted using the discotic liquid crystal and to be bent in the
normal line direction.
[0018] According to another embodiment, an electrophoretic display
apparatus includes a first substrate, an electrophoretic layer that
is arranged on one surface side of the first substrate, and a light
guide member that is arranged on the electrophoretic layer on a
side opposite to the first substrate, and configured to emit light
from the electrophoretic layer along a thickness direction of the
electrophoretic layer.
[0019] In the electrophoretic display apparatus according to this
embodiment, it is possible to take light at greater than the
critical angle in light scattered in the electrophoretic layer to
the outside in the normal line direction (thickness direction of
the electrophoretic layer) using the light guide member. Therefore,
it is possible to reduce light which is totally reflected and
radiates adjacent pixels when the light guide member is not
provided. Therefore, display irregularity due to optical crosstalk
may be prevented from occurring and it is possible to perform
display with a higher quality.
[0020] According to another embodiment, there is provided an
electronic apparatus including the electrophoretic display
apparatus according to at least one previously described
embodiment.
[0021] In the electronic apparatus according to this embodiment,
the electrophoretic display apparatus is included, with the result
that display irregularity may be prevented in the electronic
apparatus itself and thus perform display with a higher
quality.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] Non-limiting and non-exhaustive embodiments of the present
disclosure will be described with reference to the accompanying
drawings, wherein like numbers reference like elements.
[0023] FIG. 1 is a cross-sectional diagram illustrating the
schematic configuration of an electrophoretic display apparatus
according to at least one embodiment.
[0024] FIG. 2 is a schematic cross-sectional diagram illustrating a
phenomenon which is generated in an electrophoretic display
apparatus according to conventional art.
[0025] FIG. 3 is a graph illustrating an Equation 1.
[0026] FIG. 4 is a cross-sectional diagram illustrating the
schematic configuration of an optical element.
[0027] FIG. 5 is a cross-sectional diagram illustrating the
schematic configuration of an electrophoretic display apparatus
according to another embodiment.
[0028] FIG. 6 is an explanatory diagram illustrating arrangement
pitch of an optical fiber on a fiber plate.
[0029] FIG. 7 is a diagram illustrating the schematic configuration
of an electrophoretic display apparatus according to another
embodiment.
[0030] FIG. 8A is a perspective diagram illustrating an electronic
book as an example of an electronic apparatus.
[0031] FIG. 8B is a perspective diagram illustrating a wristwatch
as an example of an electronic apparatus.
[0032] FIG. 8C is a perspective diagram illustrating an electronic
paper as an example of an electronic apparatus.
DESCRIPTION OF EXEMPLARY EMBODIMENTS
[0033] Hereinafter, an electrophoretic display apparatus and an
electronic apparatus according to embodiments of the disclosure
will be described with reference to the accompanying drawings. It
is to be understood, however, that other embodiments may be
utilized and changes may be made without departing from the scope
of the present disclosure. Therefore, the following detailed
description is not to be taken in a limiting sense, and the scope
of the present disclosure is defined by the appended claims and
their equivalents.
[0034] For ease in understanding, some sections of the drawings
referred to in the description below are enlarged and shown for
convenience, and the ratio of the dimension of each component or
the like is not limited to the actual dimension.
[0035] FIG. 1 is a cross-sectional diagram illustrating the
schematic configuration of an electrophoretic display apparatus
according to a first embodiment. As shown in FIG. 1, an
electrophoretic display apparatus 100 includes an element substrate
1, a counter substrate 2, and an electrophoretic layer 11 which is
arranged between the element substrate 1 and the counter substrate
2.
[0036] The element substrate (first substrate) 1 includes a
substrate material 1A, pixel electrodes (first electrodes) 4 which
are provided on a side of the electrophoretic layer 11 of the
substrate material 1A, and a first insulation film 7 which covers
the pixel electrodes 4. The substrate material 1A is a substrate
which is formed of glass, plastic, or the like, and may not be
transparent because the substrate material 1A is arranged on a side
opposite to the image display surface. The pixel electrodes 4 are
acquired by laminating a nickel plate and a metal plate on a Cu
foil in this order, and correspond to electrodes which are formed
by Al, Indium Tin Oxide (ITO), or the like. Although not shown in
the drawing, scan lines, data lines, selection transistors, and the
like are formed between the pixel electrodes 4 and the substrate
material 1A.
[0037] The counter substrate (second substrate) 2 is formed of a
transparent substrate material, such as glass or plastic, and is
arranged on a side of the image display. A planar-shaped common
electrode 5, which faces the plurality of pixel electrodes 4, is
formed on the side of the electrophoretic layer 11 of the counter
substrate 2. The entire surface of the common electrode 5 is
covered by a second insulation film 8. The common electrode 5 is a
transparent electrode which is formed of MgAg, ITO, IZO
(indium/zinc oxide), or the like.
[0038] The electrophoretic layer 11 is filled in spaces which are
divided by a first insulation film 7 which is provided on an inner
surface side of the element substrate 1, a second insulation film 8
which is provided on an inner surface side of the counter substrate
2, and the walls 10 which are provided between the first insulation
film 7 and the second insulation film 8. The walls 10 perform
division on pixels G which are provided to correspond to the
respective pixel electrodes 4, and are formed of a transparent
material (an acryl or epoxy resin or the like).
[0039] The thickness of the walls 10 is, for example, 30 .mu.m.
Meanwhile, a junction layer 21 is provided between the upper sides
of the walls 10 and the second insulation film 8. The junction
layer 21 is provided to connect the counter substrate 2 to the
element substrate 1 on which the walls 10 are formed. The junction
layer 21 is formed of, for example, a transparent resin, and the
upper sides of the walls 10 are encroached by the junction layer
21. The thickness of the junction layer 21 may be to an extent
which does not hinder an electric field, and may be, for example, 2
.mu.m to 6 .mu.m. In addition, the amount of the walls 10 which are
encroached by the junction layer 21 may be, for example, 0.5 .mu.m
to 1 .mu.m.
[0040] The electrophoretic layer 11 includes a plurality of
electrophoretic particles 31 which are dispersed in a dispersion
medium 30. In the embodiment, the electrophoretic particles 31
include, for example, white particles 31a and black particles
31b.
[0041] The white particles 31a are particles (polymer or colloid)
which are formed of, for example, a white pigment, such as titanium
dioxide, zinc oxide, or antimony trioxide, and are, for example,
negatively charged and used. The black particles 31b are particles
(polymer or colloid) which are formed of, for example, a black
pigment, such as aniline black or carbon black, and are, for
example, positively charged and used. If necessary, it is possible
to add dispersing agents, lubricants, stabilizing agents, and the
like, such as charge control agents, titanium-coupling agents,
aluminate coupling agents, and silane-based coupling agents which
include particles, such as an electrolyte, a surfactant, a metallic
soap, resin, gum, oil, varnish, and compound, to the pigments.
[0042] In addition, instead of the white particles 31a and the
black particles 31b, for example, the pigments of a red color, a
green color, a blue color may be used. According to the
configuration, it is possible to provide the electrophoretic
display apparatus 100 capable of performing color display by
displaying the red color, the green color, the blue color, and the
like.
[0043] As the dispersion medium 30, it is possible to use water,
alcohol-based solvent (methanol, ethanol, isopropanol, butanol,
octanol, methyl cellosolve, or the like), ester (ethyl acetate,
butyl acetate, or the like), ketone (acetone, methyl ethyl ketone,
methyl isobutyl ketone, or the like), aliphatic hydrocarbon
(pentane, hexane, octane, or the like), alicyclic hydrocarbon
(cyclohexane, methyl cyclohexane, or the like), aromatic
hydrocarbon (benzenes having a group of benzene, toluene, xylene,
and lone chain alkyl (hexyl benzenes, heptyl benzenes, octyl
benzenes, nonyl benzenes, decyl benzenes, undecyl benzenes, dodecyl
benzenes, tridecyl benzenes, tetradecyl benzenes, or the like)),
halogenated hydrocarbon (methyl chlorides, chloroform, carbon
tetrachloride, 1,2-dichloroethane, or the like), or the like, and
other oils may be used. It is possible to use the substances
separately or as a mixture, and, further, a surfactant, such as
carboxylate, may be compounded therewith.
[0044] Based on the configuration, in the electrophoretic display
apparatus 100, for example, when a voltage is applied between the
pixel electrodes 4 and the common electrode 5, the electrophoretic
particles 31 (the white particles 31a and the black particles 31b)
are electrically migrated toward any of the electrodes (the pixel
electrodes 4 or the common electrode 5) according to an electric
field which is generated between the pixel electrodes 4 and the
common electrode 5. For example, if the pixel electrodes 4 are set
to negative potential when the white particles 31a have positive
charge, the white particles 31a move and gather on the sides of
(lower sides) the pixel electrodes 4, and the black color is
displayed.
[0045] However, when a certain pixel (target pixel) is focused on
in the general electrophoretic display apparatus, the colors of
peripheral pixels, that is, the brightness of the target pixel
changes due to reflectance, and thus there is a problem in that
display irregularity is generated.
[0046] FIG. 2 is a schematic cross-sectional diagram illustrating a
phenomenon which is generated in a general electrophoretic display
apparatus 100A according to the related art.
[0047] As shown in FIG. 2, in the electrophoretic display apparatus
100A, light from the outside, which is incident from a side of a
counter substrate 2A which is a display surface, is scattered and
reflected in the electrophoretic layer 11A. Light which is
scattered and reflected in the electrophoretic layer 11A is
incident into the counter substrate 2A again, some light L1a of
light L1 having an angle, which is less than a critical angle, is
reflected in the boundary surface between the counter substrate 2A
and air and returns to the inside, some remaining light L1b is
emitted from the display surface as image light. In contrast, light
L2 having an angle, which is equal to or greater than the critical
angle, is totally reflected and is radiated in the electrophoretic
layer 11A again.
[0048] In the electrophoretic display apparatus 100A described
above, for example, a percentage of light reflected in the
electrophoretic layer 11A that is directly emitted from the display
surface is approximately 38%, and a percentage of light that is
returned to the inside of the display surface is approximately 62%.
Meanwhile, light which returns to the inside of the display surface
is repeatedly reflected in the electrophoretic layer 11A again.
[0049] Light emitted from some spots of the electrophoretic layer
11A returns to other spots of the electrophoretic layer 11A. That
is, it is possible to say that 62% of the brightness corresponding
to some of the electrophoretic layer 11A is from the reflection
light of remaining electrophoretic layer 11A.
[0050] Here, when it is assumed that the reflectance of the
electrophoretic layer 11 is R.sub.p and the light emission rate of
light from the display surface (that is, the reflectance of the
electrophoretic layer 11 over the counter substrate 2) is
R.sub.obs, the following Expression (1) is defined:
R.sub.obs=0.95(0.38R.sub.p/(1-0.62R.sub.p)) (1)
[0051] Meanwhile, 0.95 which is the first term on the right side of
the Expression (1) is acquired by taking reflectance of incident
light on the surface of the counter substrate 2 into
consideration.
[0052] FIG. 3 is a graph illustrating the Expression (1).
Meanwhile, in FIG. 3, a horizontal axis indicates the reflectance
R.sub.p of the electrophoretic layer 11A and a vertical axis
indicates a rate of emission of light R.sub.obs from the display
surface.
[0053] As shown in FIG. 3, if the reflectance R.sub.p of the
electrophoretic layer 11A falls, the rate of emission of light from
the display surface is rapidly lowered. The reason for this may be
that reflection of light from another position decreases as much as
the reflectance R.sub.p. That is, if the peripheral pixels of a
pixel, which is a target (hereinafter, called a target pixel), are
black, the amount of light which is radiated in the target pixel
decreases, and thus the target pixel becomes dark. However, if the
peripheral pixels of the target pixel are white, the amount of
light which is radiated to the target pixel increases, and thus the
target pixel becomes bright. That is, information in which optical
crosstalk generates the display irregularity is acquired.
[0054] Based on the information, the electrophoretic display
apparatus 100 according to an embodiment includes an optical
element (refractive index variation layer) 12 which is arranged in
the counter substrate 2 on a side opposite to the electrophoretic
layer 11. As the optical element 12, for example, an element in
which a material, such as a liquid crystal, having dielectric
anisotropy is disposed such that permittivity gradually changes in
a normal line direction of the display surface of the
electrophoretic display apparatus 100 is used. Here, since the
refractive index of a transparent member which does not have
magnetism is proportional to the square root of the permittivity,
the optical element 12 changes such that the refractive index in
the normal line direction gradually increases while receding from
the electrophoretic layer 11.
[0055] FIG. 4 is a cross-sectional diagram illustrating the
schematic configuration of the optical element 12. Meanwhile, the
common electrode 5, the second insulation film 8, the junction
layer 21, and the walls 10 which are not related to the description
are not shown in FIG. 4. As shown in FIG. 4, the optical element 12
according to an embodiment is formed of a liquid crystal plate that
includes a substrate material 12b and a plurality of discotic
liquid crystal molecules 12a which are arranged in a predetermined
oriented state in the substrate material 12b. In the optical
element 12, the oriented state of the plurality of discotic liquid
crystal molecules 12a changes such that the refractive index
gradually increases while receding from the electrophoretic layer
11. More specifically, the discotic liquid crystal molecules 12a
are vertically oriented on a side of the electrophoretic layer 11
and are horizontally oriented while receding from the
electrophoretic layer 11.
[0056] The substrate material 12b is formed of, for example, a
transparent substrate material such as acryl. In at least one
embodiment, a material which has substantially the same refractive
index as the counter substrate 2 is used as the substrate material
12b. According to this, it is possible to prevent light, which is
reflected in the electrophoretic layer 11, from reflecting in the
boundary surface between the substrate material 12b and the counter
substrate 2.
[0057] In addition, in the embodiment, the refractive index of the
optical element 12 continuously changes.
[0058] According to an embodiment, when light which is scattered in
the electrophoretic layer 11 passes through the optical element 12
on the counter substrate 2, the refractive index continuously
increases while receding from the electrophoretic layer 11.
Therefore, light L of scattered light, which is incident to the
optical element 12 from directions other than the normal line
direction, is bent in the normal line direction while passing
through the optical element 12. As above, when light L from the
electrophoretic layer 11 is effectively bent, it is possible to
efficiently take light to the outside.
[0059] As such, it is possible to cause an incident angle of light
which is scattered in the electrophoretic layer 11 with regard to a
light emission surface to be greater than a critical angle. That
is, when the optical element 12 is provided, it is possible to
relieve a condition for total reflection of scattered light due to
the electrophoretic layer 11. Therefore, it is possible to suppress
scattered light which affects the display of other pixels because
the scattered light is reflected in the surface of the counter
substrate 2 when the optical element 12 is not provided.
[0060] Therefore, it is possible to reduce the percentage in which
most of the reflection light of a certain pixel, which is generated
in the general electrophoretic display apparatus 100 as described
above due to the electrophoretic layer 11, radiates other pixels.
In other words, when the optical element 12 is provided, it is
possible to reduce reflection light from other pixels, and thus it
is possible to prevent the brightness of the target pixel from
being affected even when the display state (reflectance) of the
peripheral pixels of the target pixel changes.
[0061] Since it is possible to reduce the above-described optical
crosstalk, display irregularity may be prevented from being
generated, and it is possible to perform display with a higher
quality.
[0062] In addition, in an embodiment, the refractive index of the
optical element 12 continuously changes, and thus a boundary
surface is not generated in the optical element 12. Therefore,
light is not reflected in the boundary surface in the optical
element 12. Therefore, the scattered light in the electrophoretic
layer 11 can pass through the inside of the optical element 12 and
effectively taken to the outside.
[0063] In addition, in an embodiment, the counter substrate 2 is
covered by the optical element 12, and thus it is possible to
prevent the counter substrate 2 from being damaged or the like.
[0064] In the electrophoretic display apparatus 100 according to an
embodiment described above, optical crosstalk is may be prevented
from occurring by arranging the optical element 12, which causes
scattered light from the electrophoretic layer 11 to be bent in a
direction in which the viewing angle narrows, on the side of the
display surface.
[0065] That is, the liquid crystal plate, which is included in the
optical element 12, causes liquid crystal molecules to be
horizontally oriented on the inside (side of the electrophoretic
layer 11) and then transfers the liquid crystal molecules to be
vertically oriented on a side of the boundary surface of the air
(while receding from the electrophoretic layer 11) similarly to a
viewing angle compensation film of a liquid crystal display
apparatus, and thus the liquid crystal plate is used for totally
reverse use compared to the case in which the viewing angle is
enlarged. An electrophoretic display apparatus according to another
embodiment will be described. At least one embodiment described
above is different from this embodiment in that the optical element
12 in which the refractive index gradually changes is shown as an
example of a section which relieves a condition for total
reflection in the above described embodiment but a light guide
member, which leads light from the electrophoretic layer in the
thickness direction of the electrophoretic layer and emits light,
is used in an embodiment. The same reference numerals are attached
to the same members in this embodiment, and the description thereof
is not repeated.
[0066] FIG. 5 is a cross-sectional diagram illustrating the
schematic configuration of the electrophoretic display apparatus
according to an embodiment. As shown in FIG. 5, an electrophoretic
display apparatus 200 includes an element substrate 1, a counter
substrate 2, and an electrophoretic layer 11 which is arranged
between the element substrate 1 and the counter substrate 2.
[0067] The electrophoretic display apparatus 200 according to an
embodiment includes a fiber plate (light guide member) 52 which is
arranged on the counter substrate 2 on a side opposite to the
electrophoretic layer 11.
[0068] The fiber plate 52 is configured to include a plurality of
bundled optical fibers 52a, in which a refractive index at a
central part is greater than a refractive index at a peripheral
part, with a predetermined pitch P.
[0069] FIG. 6 is a diagram illustrating an arrangement pitch
(hereinafter, simply referred to as a pitch P) between the optical
fibers 52a in the fiber plate 52. As shown in FIG. 6, the pitch P
in the fiber plate 52 may be set such that an angle .theta..sub.u,
which is a normal line of a light emission surface when light is
emitted, is equal to or less than a critical angle .theta..sub.c.
More specifically, when the thickness of the fiber plate 52 is t, P
is set such that P is equal to or less than 2ttan.theta..sub.c.
Here, the critical angle .theta..sub.c is defined to be an angle
which satisfies 1/n=sin.theta..sub.c when it is assumed that a
refractive index of the counter substrate 2 is n.
[0070] Further, an angle of light which passes through the fiber
plate 52 may be equal to or less than the critical angle
.theta..sub.c on at least the upper surface of the fiber plate 52.
Therefore, an angle .theta..sub.d of light on the lower side of the
fiber plate 52 may be greater than the critical angle
.theta..sub.c.
[0071] According to an embodiment, scattered light which is
scattered in the electrophoretic layer 11 passes through each of
the optical fibers 52a of the fiber plate 52 on the counter
substrate 2, and thus the scattered light is bent in the normal
line direction and then emitted. As above, in an embodiment, it is
possible to cause the incident angle of light, which is scattered
in the electrophoretic layer 11, with regard to the light emission
surface, to be greater than the critical angle. That is, when the
fiber plate 52 is provided, the condition for total reflection of
scattered light due to the electrophoretic layer 11 is relieved,
with the result that light is totally reflected in the counter
substrate 2, and thus it is possible to suppress light components
which contribute to display of other pixels.
[0072] In an embodiment, the above-described optical crosstalk is
reduced, with the result that display irregularity may be prevented
from occurring, and thus it is possible to perform display with a
higher quality.
[0073] Meanwhile, in an embodiment, a case in which the plurality
of optical fibers 52a are arranged with regard to one pixel G is
shown as an example. However, the embodiments are not limited
thereto. One optical fiber 52a may be arranged with regard to a
plurality of pixels G.
[0074] In addition, the disclosure is not necessarily limited to
the embodiments described herein, and various modifications can be
added in the range without departing from the gist of the
disclosure.
[0075] For example, in embodiments, a case in which the optical
element 12 or the fiber plate 52 is provided on the outside (on the
side opposite to the electrophoretic layer 11) of the counter
substrate 2 is shown as an example. However, the disclosure is not
limited thereto. As shown in FIG. 7, the optical element 12 or the
fiber plate 52 may be provided on the inner side of the counter
substrate 2. As such, it is possible to cause scattered light from
the electrophoretic layer 11 to be efficiently incident to the
optical element 12 or the fiber plate 52. According to at least one
embodiment, only the optical element 12 or the fiber plate 52 may
be provided instead of the counter substrate 2. In this case, the
optical element 12 or the fiber plate 52 has the function as the
counter substrate 2, and thus it is possible to achieve a thin
electrophoretic display apparatus.
[0076] A case in which the electrophoretic display apparatus of
each of the above described embodiments is applied to an electronic
apparatus will be described.
[0077] FIGS. 8A to 8C are perspective diagrams illustrating
detailed examples of an electronic apparatus to which the
electrophoretic display apparatus according to the embodiments are
applied.
[0078] FIG. 8A is a perspective diagram illustrating an electronic
book which is an example of an electronic apparatus. An electronic
book (electronic apparatus) 300 includes a frame 301 which has a
book shape, a cover 302 which is provided to be rotatable
(openable) with regard to the frame 301, and operation section 303,
and a display unit 304 which includes the electrophoretic display
apparatus according to the disclosure.
[0079] FIG. 8B is a perspective diagram illustrating a wristwatch
which is an example of the electronic apparatus. A wristwatch
(electronic apparatus) 400 includes a display unit 401 which
includes the electrophoretic display apparatus according to the
disclosure.
[0080] FIG. 8C is a perspective diagram illustrating electronic
paper which is an example of an electronic apparatus. Electronic
paper (electronic apparatus) 500 includes a main body section 501
which includes a rewritable sheet having the same texture and
flexibility as paper, and a display unit 502 which includes the
electrophoretic display apparatus according to the disclosure.
[0081] Since an electronic book, an electronic paper, or the like
is used to repeatedly write letters on a white background, it is
important to solve the problems of display irregularity.
[0082] Further, the range of electronic apparatus to which the
electrophoretic display apparatus according to the disclosure can
be applied is not limited thereto, and widely includes an apparatus
which uses change in color tone in sight in accordance with the
movement of charged particles.
[0083] According to the above-described electronic book 300, the
wristwatch 400, and the electronic paper 500, the electrophoretic
display apparatus according to the disclosure is used, with the
result that display irregularity may be suppressed, thereby
resulting in a high-grade electronic apparatus which can acquire
display characteristics with a higher quality and which has higher
reliability.
[0084] Also, the electronic apparatus is an example of the
electronic apparatus according to the disclosure, and does not
limit the technical range of the disclosure. For example, the
electrophoretic display apparatus according to the disclosure may
be appropriately used for a display unit of an electronic
apparatus, such as a mobile phone or a portable audio device, a
business sheet such as a manual, a text book, a workbook, an
information sheet, and the like.
[0085] The preceding is merely a description of several
embodiments. While specific embodiments and applications have been
illustrated and described, it is to be understood that the precise
configuration and components disclosed herein is illustrative only.
Having the benefit of this disclosure, various modifications,
changes, and variations will be apparent to those of ordinary skill
in the art without departing from the spirit and scope of the
principles disclosed. Thus, to the maximum extent allowed by law,
the scope of the invention is to be determined by the broadest
permissible interpretation of the following claims and their
equivalents.
* * * * *